U.S. Pat. No. 3,484,466 teaches a process in which an aromatic sulfonamide is phosgenated in the presence of an inert solvent and a catalytic amount of a hydrocarbyl isocyanate to form the corresponding arylsulfonyl isocyanate. 4-Isocyanatosulfonylbenzoate ester is listed as a compound which can be prepared by this method.
In U.S. Pat. No. 3,379,758 arylsulfonyl monoisocyanates and arylsulfonyl diisocyanates are produced by a process which comprises mixing in the range 0.degree. to 175.degree. C., phosgene and an arylsulfonylurea of the formula Ar(SO.sub.2 NHCONHR).sub.n, wherein n is one or two, R is alkyl of one to 8 carbon atoms, inclusive, and Ar is phenyl or phenylene, unsubstituted or substituted with one or two substituents selected from the class consisting of alkyl of one to 8 carbon atoms, inclusive, cycloalkyl of 3 to 8 carbon atoms, inclusive, phenyl, naphthyl, aralkyl of 7 to 10 carbon atoms, inclusive, alkoxy of one to 8 carbon atoms, inclusive, halogen, nitro, cyan, sulfo, amino, dialkylamino of 2 to 12 carbon atoms, inclusive, and alkoxycarbonyl of 2 to 8 carbon atoms, inclusive.
In U.S. Pat. No. 3,371,114 there is taught a process of converting an aromatic sulfonamide to the corresponding aromatic sulfonyl isocyanates. Phosgenation of the sulfonamide in the presence of a catalytic quantity of a hydrocarbyl isocyanate gives the desired sulfonyl isocyanate.